NOT APPLICABLE
NOT APPLICABLE
NOT APPLICABLE
This invention relates to the ejection of freshly mixed mold compound to teeth having completed dental surgery preparations. More particularly, a nozzle which ejects recently mixed and curing molding compound is ejected along a uniformly expanding solid angle for overcoming wetting-resistant surface tension between the molding compound and prepared teeth.
This invention relates to the molding step of dental surgery. To understand the molding step, it is necessary to briefly review the dentistry in which the molding step is practiced. Accordingly, a simplified summary of dentistry resulting in placement of a crown to a tooth follows.
Decay is surgically removed from a tooth or teeth, and a preparation made to receive a crown. A mold of the preparation and margin adjacent to the preparation is made in order to construct a model. Once the mold of the preparation is made, the patient receives a temporary filling and leaves the dental office.
With the patient absent, a model of the tooth or teeth is constructed. The crown is then made to fit the model of the preparation. Presuming that the model of the preparation is an exact replication of the tooth with the preparation, the prepared crown will precisely fit the surgically altered tooth of the patient. When the patient returns to the dentist""s office, the crown is first fitted to and thereafter adhered to the preparation. Reconstructive dental surgery results.
Accurate molding is extraordinarily important in this process. Unfortunately, dental preparations by their very nature are a less than optimal environment for accurate molding. Where an inaccurate mold is made, the resultant crown cannot be used. When this occurs, a new mold must be made, a new model of the tooth or teeth fabricated, a new crown constructed, and the patient asked to return at a later time to the dental office for adhering the crown to the preparation.
Molding compound is generated from an elongate syringe-like appliance having thumb depressed plungers evacuating side-by-side cylinders of base and catalyst. Paired thumb depressed plungers simultaneously eject approximately equal amounts of base and catalyst to a static mixer attached to the appliance. The static mixer mixes the base and catalyst into a mixture. As soon as the mixture is made, curing of the molding compound begins. When the molding compound is fully cured around a tooth having a preparation, a female silicone rubber mold results from which the male model of the tooth or teeth can be constructed.
Immediately before leaving the syringe-like appliance, the freshly mixed molding compound passes from the static mixer to an intra-oral tip. The intra-oral tip is typically disposed at an angle with respect to the syringe-like appliance. This tip directs the curing molding compound onto the preparation and surrounding teeth to make the mold.
The deposit of the molding compound to the surgically altered tooth at the preparation and the margin around the preparation (those portions of the tooth which have not been surgically altered) is difficult. Dentists try to direct molding compound onto the preparation and tooth margin surrounding the preparation by manipulation of the syringe-like mold mixing apparatus. These manipulations are made so that the molding compound can wet both the tooth surface and preparation interior of the tooth in order to create an accurate mold. Unfortunately, at least three factors restrict this maneuverability.
Simply stated, the mouth of the patient, which is usually being held in an (uncomfortable) open position, restricts mold mixing tool manipulation. The syringe-like appliance as maneuvered by the dentist is restricted in motion by the confines of the patient""s mouth. Secondly, the location of the surgically repaired tooth can further restrict mold mixing tool manipulation. The immediately surrounding gums, cheek, teeth and mouth structure to the surgically altered tooth further restricts manipulation of the syringe-like mold compound mixing tool. Finally, the location of the preparation on the tooth can also restrict manipulation of the mold mixing tool. For example, where the preparation is on the back side of the tooth, the injection of freshly mixed and curing molding compound can be exceedingly difficult.
I have discovered that where molding compound is not directed normally to either a preparation surface or a tooth surface, the likelihood of an imperfectly generated mold having voids increases dramatically. I attribute this to surface tension which the surface of the tooth or preparation naturally has because of the wetting of the molding compound. Where normal contact is not made, the surface tension is not broken and voids in the mold can result.
A solution to this discovered problem was not immediately apparent. Specifically, preparations in teeth and adjacent tooth surfaces are frequently at large angles one to another. Where molding compound is directed normally on one surfacexe2x80x94say a surface of the preparationxe2x80x94the molding compound can be directed substantially tangent to the preparation margin. Undesired voids can result.
The reader will understand that the discovery of a problem to be solved, as well as the solution to the problem, can constitute invention. Insofar as the problem which I have set forth relating to the wetting of teeth and preparations is not set forth in the prior art, I claim invention.
An intra-oral molding compound ejection tip is provided to provide a substantially uniform expanding solid angle of the mixed molding compound upon molding compound ejection. A prior art intra-oral tip typically includes an ejection orifice defined about an axis parallel to the direction of mold compound ejection. In a preferred embodiment, two cuts are placed in the tip at right angles to one another within the plane of the normal axis of molding compound ejection. Each of these cuts is sized with respect to the ejection orifice to produce a uniformly expanding solid angle of the ejected molding compound. This uniformly expanding solid angle of the ejected molding compound has the property of having higher normal incidence to both preparation and margin to the preparation in teeth having dental surgery. An intra-oral tip having three slits, each at 120 degree angles about the normal axis of molding compound ejection will suffice for the practice of my invention. More generally, any combination of orifices which causes molding compound to expand from a point on the intra-oral tip along a uniformly expanding solid angle of expansion exceeding one pi steradian will suffice for the practice of this invention with the preferred ejection solid angle being a hemisphere or two pi steradians. In operation, the intra-oral tip is given excursion relative to a tooth with a preparation and margin surrounding the preparation with a portion of the solid angle of molding compound ejection preferably always directed normal to a tooth or preparation surface. Improved molding compound wetting occurs.